Artist trading cards (or ATCs) are miniature works of art about the same size as modern collector cards, measuring 2.5" x 3.5" (63 x 89 mm) and are small enough to fit inside standard card-collector pockets, sleeves or sheets. Cards are produced in various media, including dry media (pencils, pens, markers, etc.), wet media (watercolor, acrylic paints, etc.), paper media (in the form of collage, papercuts, found objects, etc.) or even metals or cloth. Cards are always signed and dated by the artist on the back of the card. They are usually traded or exchanged between friends and other artists.